figured it out! replaced camera_rotation = look_rotation + recoil
with these three lines
var final_rotation = look_rotation + recoil
camera_rotation.rotation.x = final_rotation.x
player.rotation.y = final_rotation.y
also, the code you refered to "camera_rotation = look_rotation + recoil" is not the real code.
the actual code can be found here:
https://github.com/atornity/godot_recoil_system/blob/master/scripts/camera.gd#L7...
just in case you didn't know :3